1. Field of the Invention
The present invention relates to SCSI backplanes of computer systems, and more particularly to a SCSI duplex-ready backplane.
2. Description of the Related Art
SCSI (Small Computer System Interface) has become the best known and most widely used ANSI (American National Standards Institute) interface for computer systems. The goal of SCSI has been to provide reliable connectivity and a flexible, faster command-controlled interface for hard disk drives and other computer peripherals. One way of addressing the need for flexible management of SCSI devices has been upgrading a computer system adapted for a SCSI simplex mode to provide a SCSI duplex mode.
Certain SCSI backplanes or option boards of a computer system have only supported a SCSI simplex mode. In a SCSI simplex mode, a primary SCSI controller controls a single SCSI bus coupled to a set of SCSI devices. Other SCSI backplanes or option boards have supported only a SCSI duplex mode. In a SCSI duplex mode, a primary SCSI controller controls a primary SCSI bus and a secondary SCSI controller controls a secondary SCSI bus.
So far as is known, configuring a computer system from a SCSI simplex mode to a SCSI duplex mode has required a circuit board changeout. This is undesirable in terms of time and skill level required. Some computer systems have used a SCSI simplex-only backplane, or one capable of simplex only, to enable a SCSI simplex mode. A necessary step to re-configure the state of the SCSI backplane of the computer system for a SCSI duplex mode has been to remove the SCSI simplex-only backplane board and replace it with a SCSI duplex-only backplane board.
Other computer systems have used a SCSI pass-through board which connects to the SCSI backplane board to enable a SCSI simplex mode. A necessary step to re-configure the state of the SCSI backplane for a SCSI duplex mode in this case has been to remove the SCSI pass-through board and replace it with a SCSI duplex-option board. Both of the foregoing types of computer systems thus have required a circuit board changeout to configure the state of the SCSI backplane for a SCSI simplex mode or for a SCSI duplex mode.
Configuring the state of the SCSI backplane of a computer system for a SCSI simplex mode to a SCSI duplex mode has also required a significant amount of disassembly and reassembly of the chassis of the computer system. In order to changeout the SCSI pass-through board or SCSI simplex-only backplane board, it has been necessary to at least partially dis-assemble the chassis to reach the backplane. This was necessary to remove the SCSI pass-through board or the SCSI simplex-only backplane board. After the SCSI pass-though board has been replaced with a SCSI duplex-option board or the SCSI simplex-only backplane board has been replaced with a SCSI duplex-only backplane board, the chassis could then be reassembled. When replacing a SCSI simplex-only backplane, it has also been necessary to make cabling changes. For example, it was necessary to remove a cable extending from the first SCSI controller to the SCSI simplex-only backplane board, re-install the cable from the first SCSI controller, and then install a cable extending from the second SCSI controller to the SCSI duplex-only backplane board.
Further, the changeover from simplex to duplex usually required more than mere operator level knowledge. A user is typically required to order a duplex-option kit from the computer vendor, understand the instructions in the kit, and make the necessary disassembly, circuit board changeout, and reassembly to convert the state of the SCSI backplane for a SCSI simplex mode or a SCSI duplex mode. The disassembly, circuit board changeout, and reassembly has generally cost valuable system downtime.